Three-Dimensional Object Printing Apparatus And Three-Dimensional Object Printing Method

ABSTRACT

A three-dimensional object printing apparatus includes: a head having a nozzle surface; and a robot that has a base portion and an arm portion that supports the head, and changes a position of the head with respect to the base portion, in which the three-dimensional object printing apparatus is configured to execute: a first printing operation of causing the head to print an image to a three-dimensional first medium, and a second printing operation of causing the head to print a test pattern while causing the robot to change a position of the head with respect to the second medium, and a yaw angle of the head during the execution of the first printing operation and a yaw angle of the head during the execution of the second printing operation are different from each other.

The present application is based on, and claims priority from JP Application Serial Number 2021-037083, filed Mar. 9, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a three-dimensional object printing apparatus and a three-dimensional object printing method.

2. Related Art

A three-dimensional object printing apparatus that performs printing on a surface of a three-dimensional work by an ink jet method is known. For example, an apparatus described in JP-A-2014-050832 includes a robot arm and a print head fixed to a tip of the robot arm, and prints an image with an ink from the print head on a target object.

The apparatus described in JP-A-2014-050832 has a problem that when a defect such as clogging of a nozzle of the print head occurs, printing with a deteriorated image quality is performed on the object.

SUMMARY

According to an aspect of the present disclosure, there is provided a three-dimensional object printing apparatus including: a head having a nozzle surface provided with a nozzle row in which a plurality of nozzles for ejecting a liquid are arranged; and a robot that has a base portion and an arm portion that supports the head, is provided with a plurality of rotating portions from the base portion to the arm portion, and changes a position of the head with respect to the base portion by rotating the rotating portion, in which the three-dimensional object printing apparatus is configured to execute: a first printing operation of causing the head to print an image by ejecting the liquid to a three-dimensional first medium while causing the robot to change a position of the head with respect to the first medium, and a second printing operation of causing the head to print a test pattern by ejecting the liquid to a second medium while causing the robot to change a position of the head with respect to the second medium to a position different from the position during the execution of the first printing operation, and a yaw angle of the head during the execution of the first printing operation and a yaw angle of the head during the execution of the second printing operation are different from each other.

According to another aspect of the present disclosure, there is provided a three-dimensional object printing method using a head having a nozzle surface provided with a nozzle row in which a plurality of nozzles for ejecting a liquid are arranged, and a robot that has a base portion and an arm portion that supports the head, is provided with a plurality of rotating portions from the base portion to the arm portion, and changes a position of the head with respect to the base portion by rotating the rotating portion, the method including: performing a first printing operation of causing the head to print an image by ejecting the liquid to a three-dimensional first medium while causing the robot to change a position of the head with respect to the first medium; and performing a second printing operation of causing the head to print a test pattern by ejecting the liquid to a second medium while causing the robot to change a position of the head with respect to the second medium to a position different from the position during the execution of the first printing operation, and a yaw angle of the head during the execution of the first printing operation and a yaw angle of the head during the execution of the second printing operation are different from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an outline of a three-dimensional object printing apparatus according to an embodiment.

FIG. 2 is a block diagram illustrating an electrical configuration of the three-dimensional object printing apparatus according to the embodiment.

FIG. 3 is a perspective view illustrating a schematic configuration of a head unit.

FIG. 4 is a perspective view illustrating a schematic configuration of a maintenance unit.

FIG. 5 is a flowchart illustrating an operation of the three-dimensional object printing apparatus according to the embodiment.

FIG. 6 is a side view of a robot during execution of a first printing operation.

FIG. 7 is a plan view of the three-dimensional object printing apparatus during execution of the first printing operation.

FIG. 8 is a plan view of the three-dimensional object printing apparatus during execution of a maintenance operation.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, appropriate embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, dimensions and scale of each portion are appropriately different from the actual ones, and some portions are schematically illustrated for easy understanding. In addition, the scope of the present disclosure is not limited thereto unless otherwise stated to limit the present disclosure in the following description.

In the following description, for convenience, an X-axis, a Y-axis, and a Z-axis that intersect each other will be appropriately used. Further, in the following description, one direction along the X-axis is an X1 direction, and a direction opposite to the X1 direction is an X2 direction. In the same manner, directions opposite to each other along the Y-axis are a Y1 direction and a Y2 direction. Further, directions opposite to each other along the Z-axis are a Z1 direction and a Z2 direction.

Here, the X-axis, the Y-axis, and the Z-axis correspond to the coordinate axes of the world coordinate system set in a space in which a robot 2, which will be described below, is installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to a downward direction in the vertical direction. A base coordinate system using a position of the base portion 210, which will be described below, of the robot 2 as a reference is associated with the world coordinate system by calibration. In the following, for convenience, a case where an operation of the robot 2 is controlled by using the world coordinate system as a robot coordinate system will be illustrated.

The Z-axis may not be the vertical axis. Further, the X-axis, the Y-axis, and the Z-axis are typically orthogonal to each other, but the present disclosure is not limited to this, and the X-axis, the Y-axis, and the Z-axis may not be orthogonal to each other. For example, the X-axis, Y-axis, and Z-axis may intersect each other at an angle within a range equal to or more than 80° and equal to or less than 100°.

1. First Embodiment 1-1. Outline of Three-dimensional Object Printing Apparatus

FIG. 1 is a perspective view illustrating an outline of a three-dimensional object printing apparatus 1 according to an embodiment. The three-dimensional object printing apparatus 1 is an apparatus that performs printing on a surface of a three-dimensional first medium W1 by an ink jet method.

The first medium W1 has a surface WF1 as a printing target. In the example illustrated in FIG. 1, the first medium W1 is a rugby ball having a long spherical shape, and the surface WF1 is a curved surface. For example, the first medium W1 at a time of printing is supported by a structure such as a predetermined setting table, a robot hand, or a conveyor, as needed. An aspect such as a shape or a size of the first medium W1 or the surface WF1 is not limited to the example illustrated in FIG. 1, and is freely determined. Further, a position or a posture of the first medium W1 or the surface WF1 at the time of printing may be set so that printing is possible, and is freely determined without being limited to the example illustrated in FIG. 1.

As illustrated in FIG. 1, the three-dimensional object printing apparatus 1 includes the robot 2, a head unit 3, a maintenance unit 4, a controller 5, a piping portion 10, and a wiring portion 11. Hereinafter, first, the robot 2, the head unit 3, the maintenance unit 4, the controller 5, the piping portion 10, and the wiring portion 11 will be briefly described in order.

The robot 2 is a robot that changes a position and a posture of the head unit 3 in the world coordinate system. In the example illustrated in FIG. 1, the robot 2 is a so-called 6-axis vertical articulated robot.

As illustrated in FIG. 1, the robot 2 has a base portion 210 and an arm portion 220.

The base portion 210 is a base that supports the arm portion 220. In the example illustrated in FIG. 1, the base portion 210 is fixed to a floor surface facing the Z1 direction or an installation surface such as a base plate by screwing or the like. The installation surface to which the base portion 210 is fixed may be a surface facing in any direction, is not limited to the example illustrated in FIG. 1, and may be, for example, a surface provided by a wall, a ceiling, a movable trolley, or the like. Further, in the following, when viewed in a direction perpendicular to the installation surface of the base portion 210, that is, viewed in the Z1 direction or the Z2 direction in the present embodiment is referred to as a “plan view of the base portion 210” or simply a “plan view”, in some cases.

The arm portion 220 is a 6-axis robot arm having a base end attached to the base portion 210 and a tip that changes a position and a posture three-dimensionally with respect to the base end. Specifically, the arm portion 220 has arms 221, 222, 223, 224, 225, and 226, which are coupled in this order.

The arm 221 is rotatably coupled to the base portion 210 around a rotation axis O1 via a joint portion 230_1. The arm 222 is rotatably coupled to the arm 221 around a rotation axis O2 via a joint portion 230_2. The arm 223 is rotatably coupled to the arm 222 around a rotation axis O3 via a joint portion 230_3. The arm 224 is rotatably coupled to the arm 223 around a rotation axis O4 via a joint portion 230_4. The arm 225 is rotatably coupled to the arm 224 around a rotation axis O5 via a joint portion 230_5. The arm 226 is rotatably coupled to the arm 225 around a rotation axis O6 via a joint portion 230_6.

Each of the joint portions 230_1 to 230_6 is an example of a “rotating portion”, and is a mechanism for rotatably coupling one of two adjacent members of the base portion 210 and the arms 221 to 226 to the other. Here, among the joint portions 230_1 to 230_6, the joint portion 230_1 which is closest to the base portion 210 is an example of a “first rotating portion”. Further, the joint portion 230_6 which is farthest from the base portion 210 among the joint portions 230_1 to 230_6 is an example of a “second rotating portion”. In the following, each of the joint portions 230_1 to 230_6 may be referred to as a “joint portion 230”.

Although not illustrated in FIG. 1, each of the joint portions 230_1 to 230_6 is provided with a drive mechanism for rotating one of the two adjacent members corresponding to each other to the other. The drive mechanism includes, for example, a motor that generates a drive force for the rotation, a speed reducer that decelerates and outputs the drive force, an encoder such as a rotary encoder that detects a movement amount such as an angle of the rotation, and the like. An aggregation of the drive mechanisms of the joint portions 230_1 to 230_6 corresponds to an arm drive mechanism 2 a illustrated in FIG. 2, which will be described below.

The rotation axis O1 is an axis perpendicular to the installation surface (not illustrated) to which the base portion 210 is fixed. The rotation axis O2 is an axis perpendicular to the rotation axis O1. The rotation axis O3 is an axis parallel with the rotation axis O2. The rotation axis O4 is an axis perpendicular to the rotation axis O3. The rotation axis O5 is an axis perpendicular to the rotation axis O4. The rotation axis O6 is an axis perpendicular to the rotation axis O5.

Regarding these rotation axes, “perpendicular” includes that an angle formed by the two rotation axes is strictly 90°, and the angle formed by the two rotation axes deviates within a range of approximately 90° to ±5°. In the same manner, “parallel” includes not only a case where the two rotation axes are strictly parallel with each other, but also a case where one of the two rotation axes is tilted within a range of approximately ±5° with respect to the other.

The head unit 3 is attached to the arm 226 located at the most tip of the arm portion 220 of the above robot 2 in a state of being fixed by screwing or the like, as an end effector.

The head unit 3 is an assembly having a head 3 a that ejects an ink, which is an example of a “liquid”, toward the first medium W1. In the present embodiment, the head unit 3 includes a pressure regulating valve 3 b, a curing light source 3 c, a distance sensor 3 d, and an imaging device 3 g, in addition to the head 3 a. Details of the head unit 3 will be described with reference to FIG. 3, which will be described below.

The ink is not particularly limited, and includes, for example, an aqueous ink in which a coloring material such as a dye or a pigment is dissolved in an aqueous solvent, a curable ink using a curable resin such as an ultraviolet curable type, a solvent-based ink in which a coloring material such as a dye or a pigment is dissolved in an organic solvent, and the like. Among the inks, the curable ink is preferably used. The curable ink is not particularly limited, and may be, for example, any of a thermosetting type, a photocurable type, a radiation curable type, an electron beam curable type, or the like, and a photocurable type such as an ultraviolet curable type is preferable. The ink is not limited to the solution, and may be an ink in which a coloring material or the like is dispersed as a dispersant in a dispersion medium. Further, the ink is not limited to an ink containing a coloring material, and may be, for example, an ink containing conductive particles such as metal particles for forming wiring or the like as a dispersant, a clear ink, or a treatment liquid for surface treatment of the first medium W1.

Each of the piping portion 10 and the wiring portion 11 is coupled to the head unit 3. The piping portion 10 is a pipe or a pipe group including a supply pipe 10 a that supplies an ink from an ink tank (not illustrated) to the head unit 3. The supply pipe 10 a is a flexible pipe body made of, for example, a rubber material or an elastomer material. The wiring portion 11 is a wiring or a wiring group including a drive wiring 11 a for supplying an electrical signal for driving the head 3 a. The drive wiring 11 a is configured with, for example, various flexible electrical wirings. In addition to the supply pipe 10 a, the piping portion 10 may include other pipes such as a pipe for transferring the ink ejected from the head unit 3, for example. Further, in addition to the drive wiring 11 a, the wiring portion 11 appropriately includes various wirings for transmitting other electronic signals such as a control signal SI, which will be described below, which are necessary for an operation of the head unit 3, for example.

Each of the piping portion 10 and the wiring portion 11 is fixed to the head unit 3 at a fixed position FX1 by being coupled to the head unit 3. The fixed position FX1 is a position in the end effector, specifically, a position of a connector (not illustrated) for coupling the piping portion 10 and the wiring portion 11 to the head unit 3. Further, each of the piping portion 10 and the wiring portion 11 is fixed to the arm portion 220 of the robot 2 described above by a binding band or the like at fixed positions FX2, FX3, and FX4. The fixed position FX2 is a position on the arm 224 described above. The fixed position FX3 is a position on the arm 223 described above. The fixed position FX4 is a position on the arm 222 described above. By partially fixing the piping portion 10 and the wiring portion 11 to a plurality of positions of the arm portion 220 in this manner, a positional relationship between the arm portion 220, the piping portion 10, and the wiring portion 11 can be maintained within a predetermined range while sufficiently allowing a movement of the arm portion 220. The example in FIG. 1 includes a configuration in which routing routes of the piping portion 10 and the wiring portion 11 are identical to each other, and may include a configuration in which the routing routes of the piping portion 10 and the wiring portion 11 are different from each other.

The maintenance unit 4 is a mechanism for performing maintenance on the head 3 a of the head unit 3. In the example illustrated in FIG. 1, the maintenance unit 4 has a case 4 a, a cap portion 4 b, a support table 4 c, a suction mechanism 4 d, a wiper portion 4 e, and an inspection portion 4 f. The case 4 a supports the cap portion 4 b, the support table 4 c, the suction mechanism 4 d, and the wiper portion 4 e. The cap portion 4 b covers a nozzle surface F, which will be described below, of the head 3 a. The support table 4 c biases the cap portion 4 b toward the nozzle surface F, which will be described below, of the head 3 a. The suction mechanism 4 d depressurizes a space formed between the cap portion 4 b and the nozzle surface F, which will be described below, of the head 3 a. The wiper portion 4 e wipes the nozzle surface F, which will be described below, of the head 3 a. The inspection portion 4 f supports a second medium W2 such as a paper or a film having a surface WF2 for printing a test pattern for inspecting an ink ejection function of the head 3 a. Details of the maintenance unit 4 will be described with reference to FIG. 3, which will be described below.

The controller 5 is a robot controller that controls a drive of the robot 2. Hereinafter, an electrical configuration of the three-dimensional object printing apparatus 1 will be described with reference to FIG. 2, including a detailed description of the controller 5.

1-2. Electrical Configuration of Three-dimensional Object Printing Apparatus

FIG. 2 is a block diagram illustrating an electrical configuration of the three-dimensional object printing apparatus 1 according to the embodiment. In FIG. 2, among components of the three-dimensional object printing apparatus 1, electrical components are illustrated. As illustrated in FIG. 2, in addition to the components illustrated in FIG. 1 described above, the three-dimensional object printing apparatus 1 includes a control module 6 that is communicably connected to the controller 5 and a computer 7 that is communicably connected to the controller 5 and the control module 6 Hereinafter, before the detailed description of the controller 5, the control module 6 and the computer 7 will be described in this order.

Each electrical component illustrated in FIG. 2 may be appropriately divided, a part thereof may be included in another component, or may be integrally formed with the other component. For example, a part or all of functions of the controller 5 or the control module 6 may be realized by the computer 7, or may be realized by another external device such as a personal computer (PC) connected to the controller 5 via a network such as a local area network (LAN) or the Internet.

The controller 5 has a function of controlling the drive of the robot 2 and a function of generating a signal D3 for synchronizing an ink ejection operation of the head unit 3 with the operation of the robot 2. The controller 5 according to the present embodiment also has a function of controlling a drive of the maintenance unit 4, and the function may be realized by another apparatus such as the computer 7.

The controller 5 has a storage circuit 5 a and a processing circuit 5 b.

The storage circuit 5 a stores various programs to be executed by the processing circuit 5 b and various types of data to be processed by the processing circuit 5 b. The storage circuit 5 a includes, for example, one or both semiconductor memories of a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) or a programmable ROM (PROM). A part or all of the storage circuit 5 a may be included in the processing circuit 5 b.

Route information Da is stored in the storage circuit 5 a. The route information Da is information indicating a route in which the head unit 3 is to be moved and a posture of the head unit 3 in the route. Here, as the information indicating the route and the posture, the route information Da includes information indicating a movement route and a posture of the head unit 3 when printing on the first medium W1, and information indicating a movement route and a posture between a position of the head unit 3 during the printing and a position during maintenance by the maintenance unit 4. The route information Da is determined based on, for example, a shape of the first medium W1, and is expressed by using coordinate values of the base coordinate system or the world coordinate system. The shape of the first medium W1 is determined by, for example, computer-aided design (CAD) data illustrating a three-dimensional shape of the first medium W1. The above route information Da is input from the computer 7 to the storage circuit 5 a.

The processing circuit 5 b controls an operation of the arm drive mechanism 2 a of the robot 2 based on the route information Da, and generates the signal D3. The processing circuit 5 b includes, for example, one or more processors such as a central processing unit (CPU). The processing circuit 5 b may include a programmable logic device such as a field-programmable gate array (FPGA), instead of the CPU or in addition to the CPU.

Here, the arm drive mechanism 2 a is an aggregation of the drive mechanisms of the joint portions 230_1 to 230_6 described above, and includes a motor for driving the joint portion of the robot 2 and an encoder that measures a rotation angle of the joint portion of the robot 2, for each joint portion.

The processing circuit 5 b performs inverse kinematics calculation, which is a calculation for converting the route information Da into a movement amount such as a rotation angle and a rotation speed of each joint of the robot 2. The processing circuit 5 b outputs a control signal Ski based on an output D1 from each encoder of the arm drive mechanism 2 a so that the movement amount such as the actual rotation angle and rotation speed of each of the joints becomes the above-described calculation result based on the route information Da. The control signal Ski controls a drive of the motor of the arm drive mechanism 2 a. Here, the control signal Ski is corrected by the processing circuit 5 b based on an output from the distance sensor 3 d, as needed.

Further, the processing circuit 5 b generates the signal D3, based on the output D1 from at least one of a plurality of encoders of the arm drive mechanism 2 a. For example, the processing circuit 5 b generates a trigger signal including a pulse at a timing at which the output D1 from one of the plurality of encoders becomes a predetermined value as the signal D3.

The control module 6 is a circuit that controls the ink ejection operation of the head unit 3, based on the signal D3 output from the controller 5 and print data from the computer 7. The control module 6 includes a timing signal generation circuit 6 a, a power supply circuit 6 b, a control circuit 6 c, and a drive signal generation circuit 6 d.

The timing signal generation circuit 6 a generates a timing signal PTS based on the signal D3. The timing signal generation circuit 6 a is configured with, for example, a timer that starts generation of the timing signal PTS by using detection of the signal D3 as a trigger.

The power supply circuit 6 b receives power from a commercial power source (not illustrated) to generate various predetermined potentials. The various generated potentials are appropriately supplied to each portion of the control module 6 and the head unit 3. For example, the power supply circuit 6 b generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 3. Further, the power supply potential VHV is supplied to the drive signal generation circuit 6 d.

The control circuit 6 c generates a control signal SI, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG, based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Among these signals, the waveform designation signal dCom is input to the drive signal generation circuit 6 d, and the other signals are input to the switch circuit 3 e of the head unit 3.

The control signal SI is a digital signal for designating an operation state of a drive element included in the head 3 a of the head unit 3. Specifically, the control signal SI designates whether or not to supply a drive signal Com, which will be described below, to the drive element. With this designation, for example, whether or not to eject inks from a nozzle corresponding to the drive element is designated, and the amount of ink ejected from the nozzle is designated. The waveform designation signal dCom is a digital signal for defining a waveform of the drive signal Com. The latch signal LAT and the change signal CNG are used in combination with the control signal SI, and by defining a drive timing of the drive element, an ejection timing of the ink from the nozzle is defined. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

The above control circuit 6 c includes, for example, one or more processors such as a central processing unit (CPU). The control circuit 6 c may include a programmable logic device such as a field-programmable gate array (FPGA), instead of the CPU or in addition to the CPU.

The drive signal generation circuit 6 d is a circuit that generates the drive signal Com for driving each drive element included in the head 3 a of the head unit 3. Specifically, the drive signal generation circuit 6 d includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 6 d, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 6 c from a digital signal to an analog signal, and the amplifier circuit uses the power supply potential VHV from the power supply circuit 6 b to amplify the analog signal and generate the drive signal Com. Here, among waveforms included in the drive signal Com, a signal of a waveform actually supplied to the drive element is a drive pulse PD. The drive pulse PD is supplied to the drive element from the drive signal generation circuit 6 d via the switch circuit 3 e of the head unit 3.

Here, the switch circuit 3 e is a circuit that switches whether or not to supply at least a part of the waveform included in the drive signal Com as the drive pulse PD, based on the control signal SI.

The computer 7 has a function of supplying information such as the route information Da to the controller 5, and a function of supplying information such as the print data to the control module 6. In addition to these functions, the computer 7 according to the present embodiment includes a function of controlling a drive of the curing light source 3 c, and a function of analyzing a printing result of the test pattern based on an imaging result of the imaging device 3 g, and displaying the analysis result on a display apparatus (not shown) or inputting the analysis result to the controller 5. The computer 7 is, for example, a desktop computer or a notebook computer in which a program that realizes these functions is installed.

1-3. Head Unit Configuration

FIG. 3 is a perspective view illustrating a schematic configuration of the head unit 3. In the following description, for convenience, an a-axis, a b-axis, and a c-axis that intersect with each other will be appropriately used. Further, in the following description, one direction along the a-axis is an a1 direction, and a direction opposite to the a1 direction is an a2 direction. In the same manner, directions opposite to each other along the b-axis are a b1 direction and a b2 direction. Further, directions opposite to each other along the c-axis are a c1 direction and a c2 direction.

Here, the a-axis, the b-axis, and the c-axis correspond to the coordinate axes of a tool coordinate system set in the head unit 3, and relative positions and relationships of postures with the above-described world coordinate system or robot coordinate system are changed by the operation of the above-described robot 2. In the example illustrated in FIG. 3, the c-axis is an axis parallel with the above-described rotation axis O6. The a-axis, the b-axis, and the c-axis are typically orthogonal to each other without being limited thereto, and may intersect at an angle within a range of 80° or more and 100° or less, for example. The tool coordinate system and the base coordinate system or the robot coordinate system are associated with each other by calibration. Further, the tool coordinate system is set so that, for example, a center of the nozzle surface F, which will be described below, serves as a reference (tool center point).

As described above, the head unit 3 includes the head 3 a, the pressure regulating valve 3 b, the curing light source 3 c, the distance sensor 3 d, and the imaging device 3 g. The head 3 a, the pressure regulating valve 3 b, the curing light source 3 c, the distance sensor 3 d, and the imaging device 3 g are supported by a support body 3 f illustrated by an alternate long and short dash line in FIG. 3. In the example illustrated in FIG. 3, the number of each of the head 3 a and the pressure regulating valve 3 b included in the head unit 3 is one without being limited to the example illustrated in FIG. 3, and the number may be equal to or more than 2. Further, an installation position of the pressure regulating valve 3 b is not limited to the arm 226, and may be, for example, another arm or the like, or may be a fixed position with respect to the base portion 210.

The support body 3 f is made of, for example, a metal material or the like, and is a substantially rigid body. In FIG. 3, the support body 3 f has a planar box shape, and a shape of the support body 3 f is not particularly limited and is freely determined.

The above support body 3 f is attached to the above-described arm 226. Therefore, the head 3 a, the pressure regulating valve 3 b, the curing light source 3 c, the distance sensor 3 d, and the imaging device 3 g are collectively supported by the arm 226 with the support body 3 f. Therefore, a relative position of each of the head 3 a, the pressure regulating valve 3 b, the curing light source 3 c, the distance sensor 3 d, and the imaging device 3 g with respect to the arm 226 is fixed. In the example illustrated in FIG. 3, the pressure regulating valve 3 b is disposed at a position from the head 3 a in the c1 direction. The curing light source 3 c is disposed at a position from the head 3 a in the a2 direction. The distance sensor 3 d is disposed at a position from the head 3 a in the a1 direction. The imaging device 3 g is disposed at a position from the head 3 a in the b1 direction.

The head 3 a has the nozzle surface F and a plurality of nozzles N that are opened on the nozzle surface F. In the example illustrated in FIG. 3, a normal direction of the nozzle surface F is the c2 direction, and the plurality of nozzles N are divided into nozzle rows La and nozzle rows Lb which are arranged at intervals along the a-axis. Each of the nozzle row La and the nozzle row Lb is a set of the plurality of nozzles N linearly arranged in a direction along the b-axis. Here, the element related to each nozzle N of the nozzle row La and the element related to each nozzle N of the nozzle row Lb in the head 3 a are configured to be substantially symmetrical with each other in a direction along the a-axis. Further, an arrangement direction DN, which will be described below, is parallel with the b-axis.

The nozzle surface F in the present embodiment has a concept including both a surface formed by a nozzle plate and a surface formed by a fixing plate or a cover head. The nozzle plate is a member in which the nozzle N is opened in a plate-shaped member made of silicon (Si), metal, or the like, and the fixing plate and the cover head are members provided around the nozzle plate for the purpose of fixing or protecting the nozzle plate. The fixing plate and the cover head may not be provided depending on the configuration of the head 3 a, and the nozzle surface F illustrated in FIG. 3 is formed only by the nozzle plate.

Meanwhile, positions of the plurality of nozzles N in the nozzle row La and the plurality of nozzles N in the nozzle row Lb in the direction along the b-axis may be the same or different from each other. Further, the element related to each nozzle N of one of the nozzle row La and the nozzle row Lb may be omitted. In the following, a configuration in which the positions of the plurality of nozzles N in the nozzle row La and the plurality of nozzles N in the nozzle row Lb in the direction along the b-axis coincide with each other is exemplified.

Although not illustrated, the head 3 a has a piezoelectric element which is a drive element and a cavity for accommodating inks, for each nozzle N. Here, the piezoelectric element ejects an ink from a nozzle corresponding to the cavity by changing a pressure of the cavity corresponding to the piezoelectric element. Such a head 3 a can be obtained, for example, by bonding a plurality of substrates such as a silicon substrate appropriately processed by etching or the like with an adhesive or the like. As the drive element for ejecting the ink from the nozzle, a heater that heats the ink in the cavity may be used instead of the piezoelectric element.

As described above, the ink is supplied to the head 3 a from an ink tank (not illustrated) via the supply pipe 10 a. Here, the pressure regulating valve 3 b is interposed between the supply pipe 10 a and the head 3 a.

The pressure regulating valve 3 b is a valve mechanism that is opened and closed according to a pressure of the ink in the head 3 a. By this opening and closing, the pressure of the ink in the head 3 a is maintained at a negative pressure within a predetermined range even when a positional relationship between the head 3 a and the ink tank (not illustrated) described above changes. Therefore, a meniscus of the ink formed at the nozzle N of the head 3 a is stabilized. As a result, it is possible to prevent air bubbles from entering the nozzle N, and the ink from overflowing from the nozzle N. Further, the ink from the pressure regulating valve 3 b is appropriately distributed to a plurality of locations of the head 3 a via a branch flow path (not illustrated). Here, the ink from the ink tank (not illustrated) is transferred into the supply pipe 10 a at a predetermined pressure by a pump or the like.

The curing light source 3 c emits energy such as light, heat, electron beam, or radiation for curing or solidifying the ink on the first medium W1. For example, when the ink has ultraviolet curability, the curing light source 3 c is configured with a light emitting element such as a light emitting diode (LED) that emits ultraviolet rays. Further, the curing light source 3 c may appropriately have an optical component such as a lens for adjusting an emission direction or an emission range of energy.

The curing light source 3 c may not completely cure or completely solidify the ink on the first medium W1. In this case, for example, the ink after the energy irradiation from the curing light source 3 c may be completely cured or completely solidified by the energy from the curing light source separately installed on the installation surface of the base portion 210 of the robot 2. Further, the curing light source 3 c may be provided as needed, or may be omitted.

The distance sensor 3 d is an optical displacement sensor that measures a distance between the head 3 a and the first medium W1. The distance sensor 3 d according to the present embodiment outputs a signal according to the distance between the head 3 a and the first medium W1 in a direction along the c-axis. The distance sensor 3 d may be provided as needed or may be omitted.

The imaging device 3 g is a camera for imaging a test pattern printed on the second medium W2. The imaging device 3 g includes an imaging optical system and an imaging element. The imaging optical system is an optical system including at least one imaging lens, and may include various optical elements such as a prism, or may include a zoom lens, a focus lens, or the like. The imaging element is, for example, a charge coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like. The imaging device 3 g has a rectangular pixel region configured with a plurality of pixels of the imaging element, and is disposed so that a longitudinal direction of the pixel region is parallel with the arrangement direction DN of the plurality of nozzles N described above. Further, in the imaging device 3 g, a 2-axis or 3-axis imaging coordinate system using a position of any pixel in the pixel region as a reference is set. This imaging coordinate system is associated with the above-described base coordinate system or world coordinate system by calibration. In addition to the imaging optical system and the imaging element, the imaging device 3 g may include an illumination device that illuminates the imaging region, as needed. The illumination device is, for example, a light source including a light emitting element such as a light emitting diode (LED).

1-4. Maintenance Unit Configuration

FIG. 4 is a perspective view illustrating a schematic configuration of the maintenance unit 4. As described above, the maintenance unit 4 illustrated in FIG. 4 includes the case 4 a, the cap portion 4 b, the support table 4 c, the suction mechanism 4 d, the wiper portion 4 e, and the inspection portion 4 f.

The case 4 a is a box-shaped structure that supports the cap portion 4 b, the support table 4 c, the suction mechanism 4 d, and the wiper portion 4 e. The shape of the case 4 a is not limited to the example illustrated in FIG. 4, and is freely determined.

The cap portion 4 b is a structure having a cap 4 b 1 that covers the nozzle surface F of the head 3 a, a guide portion 4 b 2, and a biasing mechanism 4 b 3. In the example illustrated in FIG. 4, the cap portion 4 b has a longitudinal shape. The cap 4 b 1 is an elastic lid made of a rubber material, an elastomer material, or the like, and covers the nozzle surface F of the head 3 a to prevent inks in the vicinity of the nozzle N of the head 3 a from drying. The cap 4 b 1 is provided with an outer frame portion that abuts on the nozzle surface F of the head 3 a, a bottom surface that is recessed with respect to the outer frame portion in the Z2 direction, and a hole that penetrates the cap 4 b 1. In a capping operation of covering the nozzle surface F of the head 3 a with the cap portion 4 b, the outer frame portion abuts on the nozzle surface F of the head 3 a so as to surround the nozzle N provided on the nozzle surface F in the horizontal state. At this time, the bottom surface faces the nozzle surface F. The hole has one end open that is opened to the bottom surface of the recess portion and the other end open that is coupled to the suction mechanism 4 d.

The biasing mechanism 4 b 3 is a mechanism that supports the cap 4 b 1 and is biased in the Z1 direction, and is configured with an elastic body such as a spring or rubber. The guide portion 4 b 2 is a member that regulates movement of the cap 4 b 1 in a direction different from the Z direction. When the nozzle surface F of the head 3 a and the above-described outer frame portion come into contact with each other, the elastic body of the biasing mechanism 4 b 3 is elastically deformed so as to contract in the Z direction. The biasing mechanism 4 b 3 may be a mechanism such as a gas stay.

The above cap portion 4 b is supported by the support table 4 c. The support table 4 c is configured with a top surface portion 4 c 1 to which the cap portion 4 b is fixed, and a plurality of leg portions 4 c 2 that support the top surface portion 4 c 1. The top surface portion 4 c 1 is a plate-shaped member made of a metal material or the like, and the cap portion 4 b and the wiper portion 4 e are fixed to the top surface portion 4 c 1 by screwing or the like. A groove recessed in the Z2 direction is formed at the top surface portion 4 c 1.

The suction mechanism 4 d is a mechanism for reducing a pressure in the space formed between the cap portion 4 b and the nozzle surface F. Due to the reduced pressure, an ink is sucked from the nozzle N of the head 3 a in a state in which the cap portion 4 b covers the nozzle surface F, so that the ink in the nozzle N is refreshed. The suction mechanism 4 d has a decompression tank and a decompression pump (not illustrated). The decompression tank is, for example, a metal chamber having an internal space for decompression, and is disposed in the case 4 a described above. The decompression tank communicates with the hole of the cap portion 4 b described above, and also communicates with the decompression pump. The decompression pump is a mechanism for decompressing the inside of the decompression tank by discharging air from the decompression tank. Valves and the like for pressure adjustment or opening and closing are respectively provided between the decompression tank and the cap portion 4 b, and between the decompression tank and the decompression pump.

The wiper portion 4 e is a structure that is disposed at a position adjacent to the cap portion 4 b, and has a wiper 4 e 1 that wipes the nozzle surface F. In the example illustrated in FIG. 4, the wiper portion 4 e has a longitudinal shape, and is disposed to be parallel with the cap portion 4 b. Further, the wiper portion 4 e is disposed between the cap portion 4 b and the inspection portion 4 f in a plan view. The wiper 4 e 1 is an elastic blade-shaped member made of a rubber material, an elastomer material, or the like, and cleans the nozzle surface F by wiping the nozzle surface F of the head 3 a. Here, it is preferable that the tip of the wiper 4 e 1 is curved toward the cap portion 4 b. The wiper 4 e 1 is fixed to the top surface portion 4 c 1 of the support table 4 c via the support body 4 e 2 by screwing or the like. The ink removed from the nozzle surface F by the wiper portion 4 e is recovered by a recovery mechanism such as the above-described groove formed at the top surface portion 4 c 1 or a recovery tank (not illustrated).

The inspection portion 4 f is a structure that supports the second medium W2 such as paper or a film having the surface WF2 for printing a test pattern for inspecting the ink ejection function of the head 3 a. In the example illustrated in FIG. 4, the inspection portion 4 f has a box shape, and has a mounting surface 4 f 1 for mounting the second medium W2. Although not illustrated, the mounting surface 4 f 1 is provided with an element such as an adhesive layer or a sticking mechanism for fixing a position of the second medium W2. The test pattern is an image for visually determining whether or not there is a defect such as clogging of the nozzle N of the head 3 a or determining whether or not there is the defect based on an imaging result of the imaging device 3 g. Contents of the test pattern may be any contents as long as the determination can be made.

In the above maintenance unit 4, the cap portion 4 b, the wiper portion 4 e, and the inspection portion 4 f are arranged in this order along a line segment perpendicular to the rotation axis O1 of the robot 2, in a plan view of the mounting surface 4 f 1. Therefore, as will be described below, with operations of the three joint portions 230 in the same manner as a first printing operation, a capping operation, a wiping operation, and a second printing operation can be smoothly performed in this order.

1-5. Operation of Three-dimensional Object Printing Apparatus 1

FIG. 5 is a flowchart illustrating an operation of the three-dimensional object printing apparatus 1 according to the embodiment. First, as illustrated in FIG. 5, the three-dimensional object printing apparatus 1 determines whether or not there is a first printing instruction, in step S1. For example, for this determination, the processing circuit 5 b determines whether or not the computer 7 instructs printing execution on the first medium W1.

When the first printing instruction is given, the three-dimensional object printing apparatus 1 performs a movement operation in step S2. This movement operation is an operation of moving the head 3 a to an execution start position of the first printing operation, which will be described below, and is performed by the processing circuit 5 b controlling the drive of the robot 2 based on the route information Da.

After step S2, the three-dimensional object printing apparatus 1 performs the first printing operation in step S3. This first printing operation is an operation of printing on the first medium W1 with inks from the head 3 a, and is performed by the processing circuit 5 b controlling the drive of the robot 2 based on the route information Da, and the control module 6 controlling the drive of the head 3 a.

After step S3, or when there is no first printing instruction, the three-dimensional object printing apparatus 1 determines whether or not there is a second printing instruction, in step S4. For example, for this determination, the processing circuit 5 b determines whether or not the computer 7 instructs printing execution on the second medium W2. When the first printing instruction is not given for a predetermined time or more, the processing circuit 5 b may determine that the second printing instruction is given, regardless of whether or not there is the execution instruction for printing on the second medium W2 from the computer 7.

When there is no second printing instruction, the three-dimensional object printing apparatus 1 returns to step S1 described above. On the other hand, when there is the second printing instruction, the three-dimensional object printing apparatus 1 performs a movement operation in step S5. This movement operation is an operation of moving the head 3 a to an execution start position of the capping operation, the wiping operation, or the second printing operation of a maintenance operation, which will be described below, and is performed by the processing circuit 5 b controlling the drive of the robot 2 based on the route information Da.

After step S5, the three-dimensional object printing apparatus 1 performs a maintenance operation in step S6. This maintenance operation includes step S6 a for performing the capping operation, step S6 b for performing the wiping operation, and step S6 c for performing the second printing operation.

The capping operation in step S6 a is an operation of covering the nozzle surface F of the head 3 a with the cap portion 4 b, and is performed by the processing circuit 5 b controlling the drive of the robot 2 based on the route information Da. In the capping operation, a suction operation by the suction mechanism 4 d is performed as needed. The wiping operation in step S6 b is an operation of wiping the nozzle surface F of the head 3 a with the wiper portion 4 e, and is performed by the processing circuit 5 b controlling the drive of the robot 2 based on the route information Da. The second printing operation in step S6 c is an operation of printing a test pattern on the second medium W2 on the inspection portion 4 f with inks from the head 3 a, and is performed by the processing circuit 5 b controlling the drive of the robot 2 based on the route information Da, and the control module 6 controlling the drive of the head 3 a.

Here, an execution order of these operations included in step S6 is not particularly limited, and is preferably the order of the capping operation in step S6 a, the wiping operation in step S6 b, and the second printing operation in step S6 c. In this case, after a defect such as clogging of the nozzle N is resolved by performing the suction operation together with the capping operation, inks remaining on the nozzle surface F can be removed by the wiping operation. After that, by performing the second printing operation, it is possible to determine whether or not the defect of the nozzle N is resolved based on the printing result of the test pattern. Further, since the cap portion 4 b, the wiper portion 4 e, and the inspection portion 4 f are arranged in this order as described above, the capping operation in step S6 a, the wiping operation in step S6 b, and the second printing operation in step S6 c are performed in this order, so that these operations can be smoothly performed.

In the maintenance operation, after the execution of the second printing operation, the imaging device 3 g images the test pattern on the second medium W2, and based on the imaging result, it is determined whether or not the defect of the nozzle N is resolved. When it is determined that the defect of the nozzle N is not resolved, the capping operation in step S6 a, the wiping operation in step S6 b, and the second printing operation in step S6 c are executed again in this order, as needed.

After step S6, the three-dimensional object printing apparatus 1 determines whether or not there is an end instruction, in step S7. For example, for this determination, the processing circuit 5 b determines whether or not there is an end instruction from the computer 7.

When there is no end instruction, the three-dimensional object printing apparatus 1 returns to step S1 described above, and on the other hand, when there is the end instruction, the three-dimensional object printing apparatus 1 ends the operation. In a status where defects with the nozzle N are likely to occur, such as when the ink is not ejected by the head 3 a for a relatively long time, the maintenance operation in step S6 is executed before the first printing operation in step S3. Therefore, it is preferable to check in advance that the defect of the nozzle N is resolved.

FIG. 6 is a side view of the robot 2 during execution of a first printing operation in step S3. FIG. 6 illustrates a case where printing is performed on the surface WF1 of the first medium W1 disposed so that a long axis AX of the first medium W1 having a long spherical shape is parallel with the X-axis. Here, the first medium W1 is placed at a position from the robot 2 in the X2 direction. At a posture of the head 3 a illustrated by the solid line in FIG. 6, the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel.

In the first printing operation, as illustrated in FIG. 6, the robot 2 moves the head 3 a along a movement route RU. The movement route RU is a route from a position PS to a position PE along the surface WF1. The movement route RU has a linear shape extending along the X-axis when viewed in the Z2 direction.

In the first printing operation, the robot 2 operates the three joint portions 230 among the six joint portions 230. In the example illustrated in FIG. 6, the robot 2 sets a rotation axis of each of the joint portion 230_2, the joint portion 230_3, and the joint portion 230_5 to a state of being parallel with the Y-axis during the execution of the first printing operation, and operates these joint portions. In this manner, the head 3 a can be stably moved along the movement route RU by the operation of the three joint portions 230.

Here, it is preferable that the robot 2 controls the posture of the head 3 a according to a curved surface of the surface WF1 so that a landing direction of the ink from the head 3 a on the surface WF1 is constant. Therefore, it is preferable that a yaw angle and a roll angle of the head 3 a in the movement route RU are constant. On the other hand, a pitch angle of the head 3 a in the movement route RU is preferably changed. That is, it is preferable that the pitch angles of the heads 3 a at the first position P1 and the second position P2, which are any two points in the movement route RU, are different from each other. In the present embodiment, the movement route RU is set so that an ejection direction vector of the ink droplets ejected by the head 3 a always includes a vertically downward component. In other words, a vector in the c2 direction includes a component in the Z2 direction. According to the setting of the movement route RU, the head 3 a does not eject the ink droplets in a direction against gravity, so that the ink droplets fly stably.

The printing is performed on the work W by the above printing operation.

Here, the yaw angle, the roll angle, and the pitch angle of the head 3 a will be described. The yaw angle, the roll angle, and the pitch angle of the head 3 a are expressed as the amount of rotation around the c-axis, the a-axis, and the b-axis based on a reference posture of the head 3 a set in any manner. At the reference posture of the head 3 a, relationships between the a-axis, b-axis, and c-axis and the X-axis, Y-axis, and Z-axis are uniquely fixed.

The yaw angle of the head 3 a at a first posture of the head 3 a is expressed as the amount of rotation around the c-axis required for a posture change from the reference posture to the first posture. The amount of rotation around the c-axis is an absolute value of an angle formed by the a-axis at the reference posture and the a-axis at the first posture when viewed in a direction along the c-axis at the reference posture. Alternatively, the amount of rotation around the c-axis is an absolute value of an angle formed by the b-axis at the reference posture and the b-axis at the first posture when viewed in the direction along the c-axis at the reference posture.

In the same manner, the roll angle of the head 3 a at the first posture of the head 3 a is expressed as the amount of rotation around the a-axis required for the posture change from the reference posture to the first posture. The amount of rotation around the a-axis is an absolute value of an angle formed by the b-axis at the reference posture and the b-axis at the first posture when viewed in a direction along the a-axis at the reference posture. Alternatively, the amount of rotation around the a-axis is an absolute value of an angle formed by the c-axis at the reference posture and the c-axis at the first posture when viewed in the direction along the a-axis at the reference posture.

In the same manner, the pitch angle of the head 3 a at the first posture of the head 3 a is expressed as the amount of rotation around the b-axis required for the posture change from the reference posture to the first posture. The amount of rotation around the b-axis is an absolute value of an angle formed by the a-axis at the reference posture and the a-axis at the first posture when viewed in a direction along the b-axis at the reference posture. Alternatively, the amount of rotation around the b-axis is an absolute value of an angle formed by the c-axis at the reference posture and the c-axis at the first posture when viewed in the direction along the b-axis at the reference posture.

The yaw angle, the roll angle, and the pitch angle of the head 3 a will be further described with reference to FIG. 6. For example, the reference posture of the head 3 a is set as a posture at which the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel. At this time, all the yaw angle, the roll angle, and the pitch angle of the head 3 a illustrated by a solid line in FIG. 6 are 0°. On the other hand, the pitch angle of the head 3 a illustrated by a broken line in FIG. 6 is approximately 45°, and the yaw angle and the roll angle are 0°. That is, the head 3 a illustrated by the solid line and the head 3 a illustrated by the broken line in FIG. 6 have different pitch angles.

FIG. 7 is a plan view of the three-dimensional object printing apparatus 1 during execution of the first printing operation. In a posture of the head 3 a illustrated by the solid line in FIG. 7, the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel. During the execution of the first printing operation, as illustrated in FIG. 7, in the plan view of the base portion 210, the arrangement direction DN of the plurality of nozzles N of the head 3 a is orthogonal to a scanning direction DS of the head 3 a in the above-described movement route RU. Here, when the virtual line segment coupling the head 3 a and the base portion 210 during the execution of the first printing operation in the plan view of the base portion 210 is defined as a first line segment L1, an angle θ1 formed by the arrangement direction DN and a first line segment L1 is 90°. Meanwhile, the angle θ1 is not limited to 90°, and may be, for example, in a range equal to or more than 70° and equal to or less than 110°. The first line segment L1 can be more strictly defined as a virtual line segment coupling a center point of the nozzle surface F and the rotation axis O1 during execution of a printing operation in the plan view of the base portion 210.

After executing the first printing operation, the head 3 a moves onto the cap portion 4 b by the movement operation in step S5 described above, as illustrated by an alternate long and short dash line in FIG. 7. At the posture of the head 3 a illustrated by the alternate long and short dash line in FIG. 7, the c-axis and the Z-axis are parallel, and an angle formed by the a-axis and the X-axis is 45° and an angle formed by the b-axis and the Y-axis is 45°.

Here, the reference posture of the head 3 a is set as a posture at which the a-axis and the X-axis are parallel, the b-axis and the Y-axis are parallel, and the c-axis and the Z-axis are parallel. At this time, the yaw angle, the roll angle, and the pitch angle of the head 3 a illustrated by a solid line in FIG. 7 are all 0°. On the other hand, the yaw angle of the head 3 a illustrated by the alternate long and short dash line in FIG. 7 is 45°, and the roll angle and pitch angle are 0°. That is, the yaw angle of the head 3 a illustrated by the solid line and the head 3 a illustrated by the alternate long and short dash line in FIG. 7 is different from each other. In other words, the arrangement direction DN of the nozzles N when viewed from any coordinate in the world coordinate system in the Z1 direction differs during the execution of the printing operation and after the execution of the movement operation or during the execution of the capping operation. More specifically, an angle formed by the arrangement direction DN during the printing operation and the arrangement direction DN after the movement operation or the capping operation is executed is 45°.

The movement operation is mainly performed by operating the joint portion 230_1. Here, the joint portion 230_2, the joint portion 230_3, and the joint portion 230_5 used in the above-described first printing operation may be operated, and it is preferable not to operate the joint portion 230_4 and the joint portion 230_6. In this case, when the first printing operation is performed again, reproducibility of the operation of the robot 2 in the first printing operation can be improved.

FIG. 8 is a plan view of the three-dimensional object printing apparatus 1 during execution of a maintenance operation. In FIG. 8, a state of the robot 2 during execution of a capping operation when the capping operation, a wiping operation, and a second printing operation are executed in this order is illustrated by a solid line. As illustrated in FIG. 8, when a virtual line segment coupling the head 3 a and the base portion 210 during the execution of the capping operation in the plan view of the base portion 210 is defined as a second line segment L2, an angle θ2 formed by the arrangement direction DN and the second line segment L2 is 90°. Meanwhile, the angle θ2 is not limited to 90°, and may be, for example, in a range equal to or more than 70° and equal to or less than 110°. The second line segment L2 can be more strictly defined as a virtual line segment coupling the center point of the nozzle surface F during execution of the capping operation and the rotation axis O1 in the plan view of the base portion 210.

Here, when an angle formed by the first line segment L1 and the second line segment L2 in the plan view of the base portion 210 is θ3, the angles θ1, θ2, and θ3 satisfy a relationship of |θ1−θ2|<θ3. Further, from the viewpoint of reducing twisting of the piping portion 10 and the wiring portion 11, |θ1−θ2| is preferably as small as possible.

After the capping operation is executed, the wiping operation and the second printing operation are executed in this order. At this time, the robot 2 sets the rotation axis of each of the joint portion 230_2, the joint portion 230_3, and the joint portion 230_5 to a state of being parallel with the Y-axis, and operates these joint portions, in the same manner as the first printing operation described above. In this manner, the head 3 a can be stably moved along the movement route RU by the operation of the three joint portions 230. Here, while the second printing operation is being executed, the three joint portions 230 are operated. Meanwhile, the surface WF2 of the second medium W2 is a plane, so that it is preferable that not only the yaw angle and roll angle of the head 3 a but also the pitch angle is constant, from the viewpoint of improving an image quality of the test pattern.

After executing the above maintenance operation, the head 3 a moves to the above-described printing position by the above-described movement operation in step S2, as illustrated by an alternate long and short dash line in FIG. 8. The movement operation is mainly performed by operating the joint portion 230_1, in the same manner as the movement operation in step S5.

As described above, the three-dimensional object printing apparatus 1 has the head 3 a and the robot 2. The head 3 a has the nozzle surface F at which the nozzle row La and the nozzle row Lb in which the plurality of nozzles N for ejecting an ink, which is an example of a “liquid”, are arranged are provided. The robot 2 includes the base portion 210, and the arm portion 220 that supports the head 3 a, and the joint portions 230_2 to 230_6, which are examples of a “plurality of rotating portions”, are provided from the base portion 210 to the arm portion 220 to change a position of the head 3 a with respect to the base portion 210 by rotation of the joint portions 230_2 to 230_6.

As described above, the three-dimensional object printing apparatus 1 executes the first printing operation in step S3 and the second printing operation in step S6 c. In the first printing operation in step S3, the head 3 a ejects inks to the first medium W1 to print an image while the robot 2 changes the position of the head 3 a with respect to the first medium W1. In the second printing operation in step S6 c, the head 3 a prints the test pattern by ejecting the inks to the second medium W2 while the robot 2 changes the position of the head 3 a with respect to the second medium W2 to a position different from the position during the execution of the first printing operation. Here, the yaw angle of the head 3 a during the execution of the first printing operation in step S3 and the yaw angle of the head 3 a during the execution of the second printing operation in step S6 c are different from each other.

In the above-described three-dimensional object printing apparatus 1, the test pattern is printed on the second medium W2 by executing the second printing operation, so that it is possible to determine a defect such as clogging of the nozzle N based on the printing result. Therefore, when there is the defect, the defect can be improved before the execution of the first printing operation. As a result, it is possible to prevent the first medium W1 from being printed with an image having a deteriorated image quality due to the defect by executing the first printing operation. Further, by making the yaw angles of the head 3 a different from each other between the execution of the first printing operation in step S3 and the execution of the second printing operation in step S6 c, the amount of rotation of the joint portion 230_6 closest to the head 3 a among a plurality of joint portions 230 of the robot 2 can be reduced when the head 3 a is moved between the execution positions of these operations. As a result, damage due to twisting of the wiring or the like related to the head 3 a can be reduced. Further, since the positions of the heads 3 a during the execution of the first printing operation and the second printing operation are different from each other, it is possible to perform an operation such as feeding or removing the first medium W1 during the execution of the second printing operation. Therefore, even when the second printing operation is executed, it is possible to reduce a decrease in productivity of printing on the first medium W1.

In the three-dimensional object printing apparatus 1, when the two positions through which the head 3 a passes during the execution of the first printing operation in step S3 are set as the first position P1 and the second position P2, it is preferable that the pitch angle at the first position P1 and the pitch angle at the second position P2 of the head 3 a are different from each other. In this case, even when the printing surface of the first medium W1 is a curved surface or the like, the posture of the head 3 a with respect to the target portion of the printing surface can be kept constant. Therefore, there is an advantage that the image quality can be easily improved regardless of the shape of the printing surface of the first medium W1.

Here, the first printing operation in step S3 preferably includes an operation of changing the position of the head 3 a with respect to the first medium W1 while maintaining the yaw angle and the roll angle of the head 3 a to be constant. In this case, it is possible to reduce unevenness of a density of the ink ejected from the head 3 a to the first medium W1 during the execution of the first printing operation in step S3. As a result, there is an advantage that the image quality can be easily improved.

In the same manner, the second printing operation in step S6 c preferably includes an operation of changing the position of the head 3 a with respect to the second medium W2 while maintaining the yaw angle, the roll angle, and the pitch angle of the head 3 a to be constant. In this case, it is possible to reduce unevenness of a density of the ink ejected from the head 3 a to the planar second medium W2 during the execution of the second printing operation in step S6 c. As a result, there is an advantage that the image quality of the test pattern can be easily improved. This advantage contributes to improvement of accuracy of the determination based on the printing result of the test pattern.

Further, the three-dimensional object printing apparatus 1 further executes the movement operation in step S2 or step S5, as described above. In the movement operation in step S2 or step S5, the robot 2 moves the head 3 a within a period between an execution period of the first printing operation in step S3 and an execution period of the second printing operation in step S6 c. Therefore, with the movement operation in step S2, the second printing operation in step S6 c can be shifted to the first printing operation in step S3 can be performed. With the movement operation in step S5, the first printing operation in step S3 is shifted to the second printing operation in step S6 c can be performed.

In addition, the amount of rotation of the joint portion 230_6 over an execution period of the movement operation in step S2 or step S5 is smaller than the amount of rotation of the joint portion 230_1 over an execution period of the movement operation in step S2 or step S5. Here, the joint portion 230_1 is an example of a “first joint portion”, and is the joint portion 230 closest to the base portion 210 among the plurality of joint portions 230. The joint portion 230_6 is an example of a “second joint portion”, and is the joint portion 230 farthest from the base portion 210 among the plurality of joint portions 230. When the joint portion 230_6 rotates, the wiring or the like such as the supply pipe 10 a and the drive wiring 11 a related to the head 3 a is more likely to be twisted than when the joint portion 230_1 rotates. Therefore, by making the amount of rotation of the joint portion 230_6 over the execution period of the movement operation in step S2 or step S5 smaller than the amount of rotation of the joint portion 230_1 over the execution period of the movement operation in step S2 or step S5, it is possible to reduce twisting of the wiring or the like in the movement operation in step S2 or step S5.

Further, a difference between the yaw angle of the head 3 a during the execution of the first printing operation in step S3 and the yaw angle of the head 3 a during the execution of the second printing operation in step S6 c is preferably equal to or more than 45°, and more preferably equal to or more than 90°. As the difference in yaw angle is larger, a position of the first medium W1 during the execution of the first printing operation in step S3 and the position of the head unit 3 during the execution of the second printing operation in step S6 c are separated from each other. Therefore, when performing an operation such as placing or removing the first medium W1 and adjusting the position of the first medium W1 during the execution of the second printing operation, it is possible to prevent the head unit 3 from interfering with this operation.

Further, as described above, the three-dimensional object printing apparatus 1 further includes the imaging device 3 g which is supported by the arm portion 220 so that a positional relationship with respect to the head 3 a is fixed, and images the test pattern. Therefore, it is possible to determine the defect of the nozzle N based on the imaging result of the imaging device 3 g.

Here, as described above, the imaging device 3 g has a rectangular pixel region configured with a plurality of pixels, and a longitudinal direction of the pixel region is parallel with the arrangement direction DN of the plurality of nozzles N. Therefore, the test pattern can be effectively imaged by the imaging device 3 g.

Further, as described above, the imaging device 3 g and the head 3 a are arranged along the arrangement direction DN of the plurality of nozzles N. Therefore, it is possible to prevent the imaging device 3 g from coming into contact with the three-dimensional first medium W1 during the execution of the first printing operation. There is another advantage that ink mist from the nozzle N is unlikely to adhere to the imaging device 3 g.

Further, the three-dimensional object printing apparatus 1 further has the cap portion 4 b, as described above. A position of the cap portion 4 b with respect to the base portion 210 is fixed, and covers the nozzle surface F. Here, the three-dimensional object printing apparatus 1 further executes the capping operation in step S6 a, as described above. In this capping operation, the robot 2 locates the head 3 a at a position at which the nozzle surface F is covered with the cap portion 4 b. Therefore, even when the first printing operation in step S3 is not executed for a long period of time, it is possible to reduce thickening or solidification of the ink on the nozzle surface F. As a result, clogging of each nozzle N due to the ink can be reduced.

Further, as described above, the yaw angle of the head 3 a during the execution of the second printing operation in step S6 c and the yaw angle of the head 3 a during the execution of the capping operation in step S6 a are equal to each other. Therefore, it is possible to simplify the operation of the robot 2 when the capping operation and the second printing operation are alternately repeated.

Further, as described above, the robot 2 moves the head 3 a in a direction orthogonal to the arrangement direction DN of the plurality of nozzles N during the execution of the capping operation, within a period between the execution period of the capping operation in step S6 a and the execution period of the second printing operation in step S6 c. Therefore, it is possible to simplify the operation of the robot 2 when the capping operation and the second printing operation are alternately repeated.

Further, the three-dimensional object printing apparatus 1 further includes the wiper portion 4 e, as described above. The wiper portion 4 e is disposed at a position adjacent to the cap portion 4 b, and wipes the nozzle surface F. Here, the three-dimensional object printing apparatus 1 further executes a wiping operation in step S6 b. In the wiping operation, the robot 2 moves the head 3 a so that the nozzle surface F is wiped by the wiper portion 4 e. Therefore, it is possible to reduce the nozzle surface F from becoming dirty due to the ink.

Here, as described above, during the execution of the capping operation in step S6 a, the cap portion 4 b, the wiper portion 4 e, and the second medium W2 are arranged in this order, along a direction orthogonal to the arrangement direction DN of the plurality of nozzles N. Therefore, the capping operation, the wiping operation, and the second printing operation can be effectively performed in this order.

Further, when the first medium W1 is a poorly absorbent medium that is less likely to absorb the liquid from the head 3 a as compared with the second medium W2, that is, the second medium W2 easily absorbs the liquid from the head 3 a as compared with the first medium W1, there is an advantage that an image quality of the test pattern can be easily improved in the second printing operation.

Further, when the surface WF1 to be printed on the first medium W1 has a three-dimensional shape, while the surface WF2 as a printing target on the second medium W2 has a planar shape, there is an advantage that not only the image quality of the test pattern can be easily improved in the second printing operation, but also accuracy of imaging the test pattern by the imaging device 3 g can be easily improved.

2. Modification Example

Each form in the above examples can be variously modified. Specific modification aspects that can be applied to each of the above-described forms are illustrated below. The two or more aspects freely selected from the following examples can be appropriately merged within a range not mutually contradictory.

2-1. Modification Example 1

In the above-described embodiment, a configuration using a 6-axis vertical multi-axis robot as a robot is exemplified, and the configuration is not limited to this configuration. The robot may be, for example, a vertical multi-axis robot other than the 6-axis robot, or a horizontal multi-axis robot. Further, the arm portion of the robot may have a telescopic mechanism or the like, in addition to the rotating portion configured with the rotating mechanism. Meanwhile, from the viewpoint of the balance between the print quality in the printing operation and the degree of freedom of the robot operation in the non-printing operation, the robot is preferably a multi-axis robot having 6 axes or more.

2-2. Modification Example 2

In the above-described embodiment, a configuration using screwing or the like as a method of fixing the head to the robot is exemplified, and the configuration is not limited to this configuration. For example, the head may be fixed to the robot by gripping the head with a gripping mechanism such as a hand mounted as an end effector of the robot.

2-3. Modification Example 3

In the above-described embodiment, a configuration in which printing is performed by using one type of ink is exemplified. Meanwhile, the configuration is not limited to this configuration, and the present disclosure can be applied to a configuration in which printing is performed by using two or more types of ink.

2-4. Modification Example 4

The application of the three-dimensional object printing apparatus of the present disclosure is not limited to printing. For example, a three-dimensional object printing apparatus that ejects a solution of a coloring material is used as a manufacturing apparatus of forming a color filter of a liquid crystal display apparatus. Further, a three-dimensional object printing apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus of forming wirings or electrodes on a wiring substrate. In addition, the three-dimensional object printing apparatus can also be used as a jet dispenser of applying a liquid such as an adhesive to a medium. 

What is claimed is:
 1. A three-dimensional object printing apparatus comprising: a head having a nozzle surface provided with a nozzle row in which a plurality of nozzles for ejecting a liquid are arranged; and a robot that has a base portion and an arm portion that supports the head, is provided with a plurality of rotating portions from the base portion to the arm portion, and changes a position of the head with respect to the base portion by rotating the rotating portion, wherein the three-dimensional object printing apparatus is configured to execute: a first printing operation of causing the head to print an image by ejecting the liquid to a three-dimensional first medium while causing the robot to change a position of the head with respect to the first medium, and a second printing operation of causing the head to print a test pattern by ejecting the liquid to a second medium while causing the robot to change a position of the head with respect to the second medium at a position different from the position during the execution of the first printing operation, and a yaw angle of the head during the execution of the first printing operation and a yaw angle of the head during the execution of the second printing operation are different from each other.
 2. The three-dimensional object printing apparatus according to claim 1, wherein when two positions through which the head passes during the execution of the first printing operation are defined as a first position and a second position, a pitch angle of the head at the first position and a pitch angle of the head at the second position are different from each other.
 3. The three-dimensional object printing apparatus according to claim 1, wherein the first printing operation includes an operation of changing the position of the head with respect to the first medium while maintaining the yaw angle and a roll angle of the head to be constant.
 4. The three-dimensional object printing apparatus according to claim 1, wherein the second printing operation includes an operation of changing the position of the head with respect to the second medium while maintaining the yaw angle, a roll angle, and a pitch angle of the head to be constant.
 5. The three-dimensional object printing apparatus according to claim 1, wherein the three-dimensional object printing apparatus is further configured to execute: a movement operation of causing the robot to move the head within a period between an execution period of the first printing operation and an execution period of the second printing operation, and when among the plurality of rotating portions, a rotating portion closest to the base portion is defined as a first rotating portion, and a rotating portion farthest from the base portion is defined as a second rotating portion, an amount of rotation of the second rotating portion over an execution period of the movement operation is smaller than an amount of rotation of the first rotating portion over the execution period of the movement operation.
 6. The three-dimensional object printing apparatus according to claim 5, wherein a difference between the yaw angle of the head during the execution of the first printing operation and the yaw angle of the head during the execution of the second printing operation is equal to or more than 45°.
 7. The three-dimensional object printing apparatus according to claim 6, wherein the difference between the yaw angle of the head during the execution of the first printing operation and the yaw angle of the head during the execution of the second printing operation is equal to or more than 90°.
 8. The three-dimensional object printing apparatus according to claim 1, further comprising: an imaging device that is supported by the arm portion so that a positional relationship with respect to the head is fixed, and images the test pattern.
 9. The three-dimensional object printing apparatus according to claim 8, wherein the imaging device has a rectangular pixel region configured with a plurality of pixels, and a longitudinal direction of the pixel region is parallel with an arrangement direction of the plurality of nozzles.
 10. The three-dimensional object printing apparatus according to claim 8, wherein the imaging device and the head are arranged along an arrangement direction of the plurality of nozzles.
 11. The three-dimensional object printing apparatus according to claim 1, further comprising: a cap portion having a position fixed with respect to the base portion, and covering the nozzle surface, wherein the three-dimensional object printing apparatus is further configured to execute: a capping operation of causing the robot to locate the head at a position at which the nozzle surface is covered with the cap portion.
 12. The three-dimensional object printing apparatus according to claim 11, wherein the yaw angle of the head during the execution of the second printing operation and a yaw angle of the head during the execution of the capping operation are equal to each other.
 13. The three-dimensional object printing apparatus according to claim 11, wherein the robot moves the head in a direction orthogonal to an arrangement direction of the plurality of nozzles during the execution of the capping operation within a period between an execution period of the capping operation and an execution period of the second printing operation.
 14. The three-dimensional object printing apparatus according to claim 11, further comprising: a wiper portion that is disposed at a position adjacent to the cap portion, and wipes the nozzle surface, wherein the three-dimensional object printing apparatus is further configured to execute: a wiping operation of causing the robot to move the head so that the nozzle surface is wiped by the wiper portion.
 15. The three-dimensional object printing apparatus according to claim 14, wherein during the execution of the capping operation, the cap portion, the wiper portion, and the second medium are arranged in this order, along a direction orthogonal to an arrangement direction of the plurality of nozzles.
 16. The three-dimensional object printing apparatus according to claim 1, wherein the first medium is a poorly absorbent medium that is less likely to absorb the liquid from the head as compared with the second medium.
 17. The three-dimensional object printing apparatus according to claim 1, wherein a surface of the first medium to be printed has a three-dimensional shape, and a surface of the second medium to be printed has a planar shape.
 18. A three-dimensional object printing method using a head having a nozzle surface provided with a nozzle row in which a plurality of nozzles for ejecting a liquid are arranged, and a robot that has a base portion and an arm portion that supports the head, is provided with a plurality of rotating portions from the base portion to the arm portion, and changes a position of the head with respect to the base portion by rotating the rotating portion, the method comprising: performing a first printing operation of causing the head to print an image by ejecting the liquid to a three-dimensional first medium while causing the robot to change a position of the head with respect to the first medium; and performing a second printing operation of causing the head to print a test pattern by ejecting the liquid to a second medium while causing the robot to change a position of the head with respect to the second medium at a position different from the position during the execution of the first printing operation, and a yaw angle of the head during the execution of the first printing operation and a yaw angle of the head during the execution of the second printing operation are different from each other. 